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Systematic (IUPAC) name
CAS number 61-00-7
ATC code N05AA04
PubChem CID 6077
DrugBank DB01614
ChemSpider 5852
Chemical data
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Mol. mass 326.456 g/mol
SMILES eMolecules & PubChem
Pharmacokinetic data
Bioavailability 6.6L/kg, high volume of distribution
Half-life 3 hours in horses
Excretion found in equine urine up to 96 hours after dosage
Therapeutic considerations
Pregnancy cat.  ?
Legal status not approved for use in cattle
Routes IV, IM, oral
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Acepromazine or acetylpromazine (more commonly known as ACP, Ace, or by the trade names Atravet or Acezine 2 , number depending on mg/ml dose) is a phenothiazine derivative antipsychotic drug. It was first used in humans in the 1950s,[1] but is now little used in humans (the closely related analogue, chlorpromazine, is still used as an antipsychotic in humans). Acepromazine is frequently used in animals as a sedative and antiemetic. Its principal value is in quietening and calming anxious animals. The standard pharmaceutical preparation, acepromazine maleate, is used extensively in horses, dogs, and cats; especially as a preanesthetic agent often in conjunction with atropine, and often an opiate such as morphine or buprenorphine. Its potential for cardiac effects can be profound and as such is not recommended for use in geriatric or debilitated animals In these cases it is often substituted with midazolam or left out of the preanesthetic medication altogether.




When used as a premedication it is commonly administered via the intramuscular route.

Potential adverse effects in dogs

It is thought that acepromazine can potentiate seizures in dogs with epilepsy. However, two recent studies have not shown an association between use of acepromazine and seizure activity, either within 36 hours of acepromazine use[2] or during hospitalization.[3]

The Boxer is reported to have a breed-related sensitivity to acepromazine. In 1996 a warning was placed in the cardiology section of the Veterinary Information Network (VIN), a US-based network for practicing veterinarians, entitled "Acepromazine and Boxers." It described several adverse reactions to acepromazine in three Boxers at the University of California at Davis veterinary teaching hospital. The reactions included collapse, respiratory arrest, and profound bradycardia (slow heart rate, less than 60 beats per minute). While there is disagreement among some veterinarians on this point, a number of veterinary publications recommend the drug be avoided in the breed.[4] Individual dogs of any breed can have a profound reaction characterized by hypotension (low blood pressure), especially if there is an underlying heart problem.

Acepromazine should be used with caution in sighthounds[4].


Acepromazine can be administered by the intramuscular route, taking effect within 30-45 minutes, or may be given intravenously, taking effect within 15 minutes. Sedation usually lasts for 1-4 hours, although some horses may feel the effects for up to 24 hours. The standard dose is highly variable, depending upon the desired effect following administration. An oral gel formulation is also available (Sedalin gel). The dosage by this route is also highly variable, but it is generally accepted that the recommended dose will give moderate sedation in most horses.

In the UK, acepromazine is not authorised for use in horses intended for human consumption.[5] In equine surgery, premedication with acepromazine is has been shown to reduce the perianaesthetic mortality rate,[6] although the reasons for this are unclear.

Additionally, acepromazine is used as a vasodilator in the treatment of laminitis, where an oral dose equivalent to "mild sedation" is commonly used, although the dose used is highly dependent on the treating veterinarian. It is also sometimes used to treat a horse experiencing Equine Exertional Rhabdomyolysis.

Precautions when using in horses

Acepromazine is a prohibited class A drug under FEI rules, and its use is prohibited or restricted by many other equestrian organizations. It can be detected in the blood for 72-120 hours, although repeated doses may make it remain present for several months.

Side effects are not common, but the use of acepromazine in stallions is usually considered contraindicated due to the risk of paraphimosis and priapism.

Acepromazine should not be used in horses dewormed with piperazine. It lowers blood pressure, and should therefore be used with caution in horses that are experiencing anemia, dehydration, shock, or colic.


  1. Collard JF, Maggs R (June 1958). "Clinical trial of acepromazine maleate in chronic schizophrenia". British Medical Journal 1 (5085): 1452–4. doi:10.1136/bmj.1.5085.1452. PMID 13536530. 
  2. Tobias KM, Marioni-Henry K, Wagner R (2006). "A retrospective study on the use of acepromazine maleate in dogs with seizures". Journal of the American Animal Hospital Association 42 (4): 283–9. PMID 16822767. http://www.jaaha.org/cgi/pmidlookup?view=long&pmid=16822767. 
  3. McConnell J, Kirby R, Rudloff E (2007). "A retrospective study on the use of acepromazine maleate in dogs with seizures". Journal of Veterinary Emergency and Critical Care 17 (3): 262–7. doi:10.1111/j.1476-4431.2007.00231.x. 
  4. 4.0 4.1 Jennifer Walker, ABC Health & Research Committee. "Acepromazine and Boxers - References". http://www.newcastleboxers.com/ace.shtml. Retrieved 2009-01-16. 
  5. NOAH, Compendium of Data Sheets for Animal Medicines (2005)
  6. GM Johnston, JK Eastment, JLN Wood, PM Taylor (2002). "The confidential enquiry into perioperative equine fatalities (CEPEF): mortality results of Phases 1 and 2". Veterinary Anaesthesia and Analgesia 29 (4): 159–70. doi:10.1046/j.1467-2995.2002.00106.x. 


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